The present invention relates to an improved refrigeration system which maintains a shell evaporator in a fully flooded condition and which unloads a hermetic compressor and which utilizes a novel control element for unloading the hermetic compressor.
By way of background, in the past in applications where a fully flooded evaporator was required, it was necessary to use certain structure such as surge drums, recirculating systems, floats, oil return piping, and oil separators. These components complicated the system in addition to adding costs thereto. Also, in the past, there were various ways of unloading a hermetic compressor when refrigeration was not required, and such methods included cycling the compressor on and off and by bypassing compressor discharge refrigerant directly into the suction line. Thus hermetic compressors were controlled in the past either by cycling the compressor on and off in response to demand or providing an artificial load with a discharge bypass valve equal to the difference between the real load and the systems capacity. Other methods included the use of pressure regulators and liquid or suction line solenoid valves controlled with thermostats. However, the various prior systems were undesirable in that they either constituted a waste of power or did not provide precise control or they involved the risk of oil starvation to the compressor.